Phase-synchronized 40 Hz tACS and iTBS effects on gamma oscillations

Area of Science:

• Neuroscience
• Cognitive Science
• Neuromodulation

Background:

• Gamma oscillations are vital for cognitive functions like memory.
• Reduced gamma activity is observed in Alzheimer's Disease (AD).
• Noninvasive brain stimulation methods are being explored to modulate brain oscillations.

Purpose of the Study:

• To investigate the effects of novel noninvasive brain stimulation techniques on gamma oscillations.
• To compare the efficacy of 40-Hz intermittent theta-burst stimulation (iTBS) and transcranial alternating current stimulation (tACS), individually and combined, in modulating gamma activity.
• To explore the potential of these interventions for conditions with attenuated gamma oscillations, such as AD.

Main Methods:

• Thirty healthy young participants underwent five conditions: 40-Hz tACS, 40-Hz iTBS, two combined iTBS-tACS protocols (peak and trough), and sham stimulation.
• Interventions targeted the dorsolateral prefrontal cortex.
• Gamma oscillatory activity was monitored for 2 hours post-intervention using electroencephalography (EEG).

Main Results:

• All stimulation protocols significantly enhanced 40-Hz oscillatory power.
• The iTBS-tACS Peak intervention demonstrated the most significant and sustained increase in gamma activity for up to 2 hours.
• 40-Hz tACS and 40-Hz iTBS showed strong acute effects (up to 30 minutes), with 40-Hz tACS showing consistent gamma induction for up to 2 hours.

Conclusions:

• Phase-synchronizing iTBS with tACS at 40 Hz, and 40-Hz tACS alone, are viable methods for inducing and stabilizing gamma oscillatory activity.
• These findings suggest potential therapeutic applications for conditions characterized by reduced gamma oscillations, like Alzheimer's Disease.